This invention relates generally to inkjet printers, and in particular to techniques for adjusting a pen-to-paper spacing.
As shown in FIG. 1, in this application a pen-to-paper spacing (PPS) is defined as the distance between a cartridge 103 of an inkjet printer and a bottom surface 118 of a media sheet 117 which is in a print zone 116 and which is supported by a platen 120 for printing. The PPS and the thickness of the media sheet 117 determine the distance between the cartridge 103 and an upper surface 119 of the media sheet 117. Maintaining a suitable distance between the cartridge 103 and the upper surface 119 is important to achieve the best image quality possible.
Normally, when the printer is manufactured, the PPS is set and fixed at a nominal value based upon a default medium having a default thickness. Nevertheless, the distance between the cartridge 103 and the upper surface 119 of the media sheet 117 may vary as media of various thicknesses are used.
Especially, when a medium thicker than the default medium is used, and if the PPS remains unchanged, the distance between the cartridge 103 and the upper surface 119 of the media sheet 117 can be relatively close. Thus, there is the possibility of the cartridge 103 contacting the upper surface 118 of the media sheet 117 during printing. This phenomenon may cause the media sheet 117 to be smeared.
However, when a medium thinner than the default medium is used and if the PPS remains unchanged, the distance between the cartridge 103 and the upper surface 119 of the media sheet 117 can be relatively far. This may affect the accurate placement of ink dots when ink drops are ejected onto the medium and consequently the printing quality as well.
Therefore, there is a need for adjusting the PPS distance in an inkjet printer.
According to a first embodiment of the invention, an inkjet printer includes a printer frame structure, a carriage movable in the printer frame structure for movement across a print zone during printing operations, and at least one cartridge mounted on the carriage for printing on a medium in the print zone. The printer further includes means for driving the cartridge between a first position in which the printer prints at a first PPS measured from a bottom surface of the medium, and a second position in which the printer prints at a second PPS.
According to a second embodiment of the invention, an inkjet printer for printing on a medium in a print zone includes a printer frame structure, a first path and a second path defined in the printer frame structure, and a carriage movable in the printer frame structure for movement across the print zone during printing operations. The carriage has a first slider for moving along one of the first and the second paths. Further more, the printer prints at a first PPS distanced from a bottom surface of the medium as the first slider moves along the first path, while prints at a second PPS distanced from said bottom surface as the first slider moves along the second path.
In an aspect of the invention, the printer includes at least one cartridge mounted on the carriage. The printer also includes means located below the cartridge for driving the cartridge relative to the printer frame structure in a direction vertical to the medium from a first position in which the printer prints at the first PPS to a second position in which the printer prints at the second PPS.
According to a second embodiment of the invention, an inkjet printer for printing on a medium in a print zone includes a printer frame structure, a carriage movable in the printer frame structure for movement across the print zone during printing operations. The carriage includes a first slider and a second slider disposed at the front and back of the carriage respectively. The printer also includes a first rail mounted on the printer frame structure and disposed at the front of the carriage for the first slider to move along with. The first rail determines a first pen-to-paper spacing distanced from a bottom surface of the medium at which spacing the printer prints as the first slider moves along the first rail. The printer further has a second rail mounted on the printer frame structure and disposed at the back of the carriage for the second slider to move along with. The second rail determines a second pen-to-paper spacing distanced from said bottom surface at which spacing the printer prints as the second slider moves along the second rail
Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.